1. Field of the Invention
The present invention relates generally to a biologically implantable prosthesis, a heart valve assembly using the prosthesis, and methods of using the same within an annulus of the body.
2. Description of the Related Art
Prosthetic heart valves can replace defective human valves in patients. Prosthetic valves commonly include sewing rings or suture cuffs that are attached to and extend around the outer circumference of the prosthetic valve orifice.
In a typical prosthetic valve implantation procedure, the heart is incised and the defective valve is removed leaving a surrounding area of locally tougher tissue. Known heart valve replacement techniques include individually passing sutures through the tough tissue to form an array of sutures. Free ends of the sutures are extended out of the thoracic cavity and laid, spaced apart, on the patient's body. The free ends of the sutures are then individually threaded through an edge around the circumference of the sewing ring. Once all sutures have been run through the ring, all the sutures are pulled up taught and the prosthetic valve is slid or “parachuted” down into place adjacent the tough tissue. Thereafter, the prosthetic valve is secured in place by traditional knot tying with the sutures.
The sewing ring is often made of a biocompatible fabric through which a needle and suture can pass. The prosthetic valves are typically sutured to a biological mass or annulus that is left when the surgeon removes the existing valve from the patient's heart. The sutures are tied snugly, thereby securing the sewing ring to the annulus and, in turn, the prosthetic valve to the heart.
Sewing rings can be tedious to secure to the valve orifice. Further, attaching the sewing ring to the annulus can be time consuming and cumbersome. The complexity of suturing provides a greater opportunity for mistakes and requires a patient to be on cardiopulmonary bypass for a lengthy period. It is also desirable to provide as large of a lumen through the prosthetic valve as possible to improve hemodynamics. However, techniques for attaching the sewing ring to the orifice typically require the area of the valve lumen be reduced to accommodate an attachment mechanism. For example, the sewing ring is typically retained on top of the annulus, resulting in a lumen that is, at the largest, the size of the original lumen.
A patient can also have a natural valve lumen that is detrimentally small. In these cases, the natural valve can be gusseted before the prosthetic valve is implanted. To gusset the natural valve, a longitudinal incision can be made along the wall of the lumen. The lumen can then be circumferentially expanded and the now-expanded incision can be covered with a patch graft or other membrane and stitched closed.
U.S. Pat. No. 4,743,253 to Magladry discloses a suture ring with a continuous compression ring. Magladry's ring is ductile, but provides a compressive, not expansive, force. In fact, the ring taught by Magladry is intended for placement over a heart valve and provides compression on the heart valve.
U.S. Pat. No. 6,217,610 to Carpentier et al. discloses an expandable annuloplasty ring. Carpentier et al. teach expanding the ring over the life of a patient by increasing the size of the ring by balloon dilatation. The ring is intended to remodel the shape of the valve annulus, not serve as a foundation to attach a second prosthesis and form a heart valve.
U.S. Pat. No. 5,984,959 to Robertson et al. discloses an expandable heart valve ring for attaching a synthetic valve thereto and a tool for attaching the ring to the synthetic valve. Robertson et al. teach the ring as having tabs that are used to attach to the second prosthesis by using a second device to engage the tabs.
There is a need for a circumferentially expandable bio-prosthesis. There is also a need for a prosthesis and method that can expand an annulus and maintain an enlarged annulus circumference. Furthermore, there is a need for a minimally invasive heart valve replacement procedure. Also, there is a need for a prosthesis that can provide for the above and engagement with a second prosthesis, for example, the crown of a heart valve. Furthermore, there is a need for the above prosthesis that can self-engage a second prosthesis to improve implantation time.